• style: Fix serialization of @namespace rule. 

    This code comes from:

https://hg.mozilla.org/mozilla-central/rev/2418cfba72c33c5623f6fb4c243c5203819c8240

I audited other callers of write_str, they seem ok.

Differential Revision: https://phabricator.services.mozilla.com/D54601
    @emilio
    emilio committed Dec 16, 2019
    d954f51